Table 4 Important genetic terms for PD risk communication.

From: Tools for communicating risk for Parkinson’s disease

Reduced penetrance

• When the probability of manifesting a disease for a particular genotype is <100% (typically defined as a lifetime risk)

• Relevant for autosomal dominant variants in LRRK2 and GBA1

Variable expression

• Describes the severity of expression of a disorder among individuals with the same genotype

• Genetic forms of Parkinson’s disease can be variable between and within families.

Residual risk

• The chance of developing a condition following a negative test result. This is due to the limitations of most genetic tests to capture all possible gene variants related to disease.

Allele

• An allele is one of two alternative forms of a given gene

• Heterozygous (variant affects only one allele) vs homozygous (identical variants on both alleles) vs compound heterozygous (both alleles have variants that are different)

Back to article page